U.S. patent application number 11/439359 was filed with the patent office on 2007-11-29 for diffusion media for seal support for improved fuel cell design.
Invention is credited to Matthew J. Beutel, Steven G. Goebel, Jeffrey A. Rock.
Application Number | 20070275288 11/439359 |
Document ID | / |
Family ID | 38622468 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070275288 |
Kind Code |
A1 |
Goebel; Steven G. ; et
al. |
November 29, 2007 |
Diffusion media for seal support for improved fuel cell design
Abstract
A fuel cell stack that includes straight cathode flow channels
and straight anode flow channels through a seal area between
bipolar plates in the stack. The fuel cell stack includes a seal
that extends around the active area of the stack and between the
stack headers and the active area. At the locations where the
cathode flow channels extend through a seal area to the cathode
input header and the cathode outlet header, and the anode flow
channels extend through a seal area to the anode input header and
the anode output header, the diffusion media layer on one side of
the membrane is extended to provide the seal load. Alternately,
shims can be used to carry the seal load.
Inventors: |
Goebel; Steven G.; (Victor,
NY) ; Beutel; Matthew J.; (Webster, NY) ;
Rock; Jeffrey A.; (Fairport, NY) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Family ID: |
38622468 |
Appl. No.: |
11/439359 |
Filed: |
May 23, 2006 |
Current U.S.
Class: |
429/434 ;
429/457; 429/469; 429/518 |
Current CPC
Class: |
H01M 8/242 20130101;
H01M 8/0273 20130101; H01M 8/2483 20160201; H01M 8/0258 20130101;
Y02E 60/50 20130101; H01M 8/0276 20130101; H01M 8/0267
20130101 |
Class at
Publication: |
429/38 ; 429/32;
429/44; 429/26; 429/35 |
International
Class: |
H01M 8/24 20060101
H01M008/24; H01M 8/10 20060101 H01M008/10; H01M 8/04 20060101
H01M008/04; H01M 2/08 20060101 H01M002/08 |
Claims
1. A fuel cell stack including a plurality of stacked fuel cells,
each fuel cell including an active area, said fuel cell stack
comprising: a plurality of membranes where each fuel cell in the
stack includes a membrane; a plurality of diffusion media layers
where each fuel cell includes an anode side diffusion media layer
at an anode side of the fuel cell and a cathode side diffusion
media layer at a cathode side of the fuel cell; a plurality of
bipolar plates positioned between the fuel cells in the stack
adjacent to the diffusion media layers, said bipolar plates
including anode flow channels facing the anode side diffusion media
layer in the fuel cells, cathode flow channels facing the cathode
side diffusion media layer in the fuel cells and cooling fluid flow
channels; an anode inlet header directing an anode reactant gas
flow to the anode flow channels; an anode outlet header receiving
the anode reactant gas flow from the anode flow channels; a cathode
inlet header directing a cathode reactant gas flow to the cathode
flow channels; a cathode outlet header receiving the cathode
reactant gas flow from the cathode flow channels; a cooling fluid
inlet header directing a cooling fluid to the cooling fluid flow
channels; a cooling fluid outlet header receiving the cooling fluid
from the cooling fluid flow channels; and a configuration of seals
for containing the reactant gas flow and the cooling fluid flow in
the stack, said configuration of seals including a cathode header
seal provided between the cathode outlet header and the active area
of each fuel cell, wherein the cathode flow channels are straight
flow channels between the cathode outlet header and the active
area, said configuration of seals further including an anode header
seal provided between the anode outlet header and the active area
of each fuel cell, wherein the anode flow channels are straight
flow channels between the anode outlet header and the active
area.
2. The fuel cell stack according to claim 1 wherein the
configuration of seals includes two separate seals between the
cooling fluid inlet header and the active area in each fuel cell,
wherein the cooling fluid flow channels are straight flow channels
through the seal area between the cooling fluid inlet header and
the active area.
3. The fuel cell stack according to claim 1 wherein the
configuration of seals includes a single piece seal having a
perimeter seal extending around each fuel cell, a seal segment
between the anode inlet header and the active area, a seal segment
between the anode outlet header and the active area, a seal segment
between the cathode inlet header and the active area and a seal
segment between the cathode outlet header and the active area.
4. The fuel cell stack according to claim 1 wherein the
configuration of seals includes a perimeter seal extending around
each fuel cell, a first seal loop extending around the anode inlet
header in each fuel cell, a second seal loop extending around the
anode outlet header in each fuel cell, a third seal loop extending
around the cathode inlet header in each fuel cell, and a fourth
seal loop extending around the cathode outlet header in each fuel
cell.
5. The fuel cell stack according to claim 4 wherein the
configuration of seals further includes a fifth seal loop extending
around the cooling fluid inlet header in each fuel cell and a sixth
seal loop extending around the cooling fluid outlet header in each
fuel cell.
6. The fuel cell stack according to claim 1 wherein the plurality
of bipolar plates are composite bipolar plates.
7. The fuel cell stack according to claim 1 wherein the plurality
of bipolar plates are stamped bipolar plates.
8. The fuel cell stack according to claim 7 wherein sections of the
stamped bipolar plates provide the configuration of seals.
9. The fuel cell stack according to claim 1 wherein the cathode
side diffusion media layer in each fuel cell extends through the
seal area between the cathode outlet header and the active area,
and wherein the anode side diffusion media layer in each fuel cell
extends through the seal area between the anode outlet header and
the active area.
10. The fuel cell stack according to claim 1 further comprising
shims positioned between the seals and the membrane at the seal
locations in the fuel cells so as to provide seal support.
11. The fuel cell stack according to claim 10 wherein the shims are
part of a fuel cell sub-gasket.
12. The fuel cell stack according to claim 10 wherein the shims in
each fuel cell combine to be a single piece shim.
13. The fuel cell stack according to claim 1 wherein the membrane
in each fuel cell extends straight through the seal area provided
by the configuration of seals.
14. The fuel cell stack according to claim 1 wherein the stack is
part of a fuel cell system on a vehicle.
15. A fuel cell stack including a plurality of stacked fuel cells,
each fuel cell including an active area, said fuel cell stack
comprising a configuration of seals, said configuration of seals
including cathode inlet header seals provided between a cathode
inlet header and an active area of each fuel cell, wherein cathode
flow channels are straight flow channels between the cathode inlet
header and the active area and wherein a cathode side diffusion
media layer in each fuel cell extends through the seal area between
the cathode inlet header and the active area, said configuration of
seals further including cathode outlet header seals provided
between a cathode outlet header and the active area of each fuel
cell, wherein the cathode flow channels are straight flow channels
between the cathode outlet header and the active area and wherein
the cathode side diffusion media layer in each fuel cell extends
through the seal area between the cathode outlet header and the
active area, said configuration of seals further including anode
inlet header seals provided between the anode inlet header and the
active area of each fuel cell, wherein anode flow channels are
straight flow channels between the anode inlet header and the
active area and wherein an anode side diffusion media layer in each
fuel cell extends through the seal area between the anode inlet
header and the active area, said configuration of seals further
including anode outlet header seals provided between an anode
outlet header and the active area of each fuel cell, wherein the
anode flow channels are straight flow channels between the anode
outlet header and the active area and wherein the anode side
diffusion media layer in each fuel cell extends through the seal
area between the anode outlet header and the active area.
16. The fuel cell stack according to claim 15 wherein the
configuration of seals includes a single piece seal having a
perimeter seal extending around each fuel cell, a seal segment
between the anode inlet header and the active area, a seal segment
between the anode outlet header and the active area, a seal segment
between the cathode inlet header and the active area and a seal
segment between the cathode outlet header and the active area.
17. The fuel cell stack according to claim 15 wherein the
configuration of seals includes a perimeter seal extending around
each fuel cell, a first seal loop extending around the anode inlet
header in each fuel cell, a second seal loop extending around the
anode outlet header in each fuel cell, a third seal loop extending
around the cathode inlet header in each fuel cell, and a fourth
seal loop extending around the cathode outlet header in each fuel
cell.
18. A fuel cell stack including a plurality of stacked fuel cells,
each fuel cell including an active area, said fuel cell stack
comprising: a plurality of membranes where each fuel cell in the
stack includes a membrane; a plurality of diffusion media layers
where each fuel cell includes an anode side diffusion media layer
at an anode side of the fuel cell and a cathode side diffusion
media layer at a cathode side of the fuel cell; a plurality of
bipolar plates positioned between the fuel cells in the stack
adjacent to the diffusion media layers, said bipolar plates
including anode flow channels facing the anode side diffusion media
layer in the fuel cells, cathode flow channels facing the cathode
side diffusion media layer in the fuel cells and cooling fluid flow
channels; an anode inlet header directing an anode reactant gas
flow to the anode flow channels; an anode outlet header receiving
the anode reactant gas flow from the anode flow channels; a cathode
inlet header directing a cathode reactant gas flow to the cathode
flow channels; a cathode outlet header receiving the cathode
reactant gas flow from the cathode flow channels; a cooling fluid
inlet header directing a cooling fluid to the cooling fluid flow
channels; a cooling fluid outlet header receiving the cooling fluid
from the cooling fluid flow channels; and a configuration of seals
for containing the reactant gas flow and the cooling fluid flow in
the stack, wherein the membrane in each fuel cell extends straight
through the seal area provided by the configuration of seals, said
configuration of seals including cathode inlet header seals
provided between the cathode inlet header and the active area of
each fuel cell, wherein the cathode flow channels are straight flow
channels between the cathode inlet header and the active area and
wherein the cathode side diffusion media layer in each fuel cell
extends through the seal area between the cathode inlet header and
the active area, said configuration of seals further including
cathode outlet header seals provided between the cathode outlet
header and the active area of each fuel cell, wherein the cathode
flow channels are straight flow channels between the cathode outlet
header and the active area and wherein the cathode side diffusion
media layer in each fuel cell extends through the seal area between
the cathode outlet header and the active area, said configuration
of seals further including anode inlet header seals provided
between the anode inlet header and the active area of each fuel
cell, wherein the anode flow channels are straight flow channels
between the anode inlet header and the active area and wherein the
anode side diffusion media layer in each fuel cell extends through
the seal area between the anode inlet header and the active area,
said configuration of seals further including anode outlet header
seals provided between the anode outlet header and the active area
of each fuel cell, wherein the anode flow channels are straight
flow channels between the anode outlet header and the active area
and wherein the anode side diffusion media layer in each fuel cell
extends through the seal area between the anode outlet header and
the active area.
19. The fuel cell stack according to claim 18 wherein the
configuration of seals further including two separate seals between
the cooling fluid inlet header and the active area in each fuel
cell, wherein the cooling fluid flow channels are straight flow
channels through the seal area between the cooling fluid inlet
header and the active area, said configuration of seals further
including two separate seals between the cooling fluid outlet
header and the active area in each fuel cell, wherein the cooling
fluid flow channels are straight flow channels through the seal
area between the cooling fluid outlet header and the active
area.
20. The fuel cell stack according to claim 18 wherein the
configuration of seals includes a single piece seal having a
perimeter seal extending around each fuel cell, a seal segment
between the anode inlet header and the active area, a seal segment
between the anode outlet header and the active area, a seal segment
between the cathode inlet header and the active area and a seal
segment between the cathode outlet header and the active area.
21. The fuel cell stack according to claim 18 wherein the
configuration of seals includes a perimeter seal extending around
each fuel cell, a first seal loop extending around the anode inlet
header in each fuel cell, a second seal loop extending around the
anode outlet header in each fuel cell, a third seal loop extending
around the cathode inlet header in each fuel cell, a fourth seal
loop extending around the cathode outlet header in each fuel cell,
a fifth seal loop extending around the cooling fluid inlet header
in each fuel cell, and a sixth seal loop extending around the
cooling fluid outlet header in each fuel cell.
22. The fuel cell stack according to claim 18 wherein the plurality
of bipolar plates are composite bipolar plates.
23. The fuel cell stack according to claim 18 wherein the plurality
of bipolar plates are stamped bipolar plates.
24. The fuel cell stack according to claim 23 wherein sections of
the stamped bipolar plates provide the configuration of seals.
25. A fuel cell stack including a plurality of stacked fuel cells,
each fuel cell including an active area, said fuel cell stack
comprising a configuration of seals, said configuration of seals
including cathode inlet header seals provided between a cathode
inlet header and an active area of each fuel cell, wherein cathode
flow channels are straight flow channels between the cathode inlet
header and the active area and wherein a shim provides seal support
at the seal area between the cathode inlet header and the active
area, said configuration of seals further including cathode outlet
header seals provided between a cathode outlet header and the
active area of each fuel cell, wherein the cathode flow channels
are straight flow channels between the cathode outlet header and
the active area and wherein a shim provides seal support at the
seal area between the cathode outlet header and the active area,
said configuration of seals further including anode inlet header
seals provided between the anode inlet header and the active area
of each fuel cell, wherein anode flow channels are straight flow
channels between the anode inlet header and the active area and
wherein a shim provides seal support at the seal area between the
anode inlet header and the active area, said configuration of seals
further including anode outlet header seals provided between an
anode outlet header and the active area of each fuel cell, wherein
the anode flow channels are straight flow channels between the
anode outlet header and the active area and wherein a shim provides
seal support at the seal area between the cathode outlet header and
the active area.
26. The fuel cell stack according to claim 25 wherein the shims are
part of a fuel cell sub-gasket.
27. The fuel cell stack according to claim 25 wherein the shims in
each fuel cell combine to be a single piece shim.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to a fuel cell stack and,
more particularly, to a fuel cell stack that includes straight
cathode and anode flow channels through a seal area of the fuel
cells in the stack so as to reduce water accumulation in the flow
channels.
[0003] 2. Discussion of the Related Art
[0004] Hydrogen is a very attractive fuel because it is clean and
can be used to efficiently produce electricity in a fuel cell. A
hydrogen fuel cell is an electro-chemical device that includes an
anode and a cathode with an electrolyte therebetween. The anode
receives hydrogen gas and the cathode receives oxygen or air. The
hydrogen gas is dissociated in the anode to generate free hydrogen
protons and electrons. The hydrogen protons pass through the
electrolyte to the cathode. The hydrogen protons react with the
oxygen and the electrons in the cathode to generate water. The
electrons from the anode cannot pass through the electrolyte, and
thus are directed through a load to perform work before being sent
to the cathode.
[0005] Proton exchange membrane fuel cells (PEMFC) are a popular
fuel cell for vehicles. The PEMFC generally includes a solid
polymer electrolyte proton conducting membrane, such as a
perfluorosulfonic acid membrane. The anode and cathode typically
include finely divided catalytic particles, usually platinum (Pt),
supported on carbon particles and mixed with an ionomer. The
catalytic mixture is deposited on opposing sides of the membrane.
The combination of the anode catalytic mixture, the cathode
catalytic mixture and the membrane define a membrane electrode
assembly (MEA). MEAs are relatively expensive to manufacture and
require certain conditions for effective operation.
[0006] Several fuel cells are typically combined in a fuel cell
stack to generate the desired power. For example, a typical fuel
cell stack for a vehicle may have two hundred or more stacked fuel
cells. The fuel cell stack receives a cathode input gas, typically
a flow of air forced through the stack by a compressor. Not all of
the oxygen is consumed by the stack and some of the air is output
as a cathode exhaust gas that may include water as a stack
by-product. The fuel cell stack also receives an anode hydrogen
input gas that flows into the anode side of the stack.
[0007] The fuel cell stack includes a series of bipolar plates
positioned between the several MEAs in the stack, where the bipolar
plates and the MEAs are positioned between two end plates. The
bipolar plates include an anode side and a cathode side for
adjacent fuel cells in the stack. Anode gas flow channels are
provided on the anode side of the bipolar plates that allow the
anode reactant gas to flow to the respective MEA. Cathode gas flow
channels are provided on the cathode side of the bipolar plates
that allow the cathode reactant gas to flow to the respective MEA.
One end plate includes anode gas flow channels, and the other end
plate includes cathode gas flow channels. The bipolar plates and
end plates are made of a conductive material, such as stainless
steel or a conductive composite. The end plates conduct the
electricity generated by the fuel cells out of the stack. The
bipolar plates also include flow channels through which a cooling
fluid flows.
[0008] Various techniques are known in the art for fabricating the
bipolar plates. In one design, the bipolar plates are made of a
composite material, such as graphite, where two plate halves are
separately molded and then glued together so that anode flow
channels are provided at one side of one of the plate halves,
cathode flow channels are provided at an opposite side of the other
plate half and cooling fluid flow channels are provided between the
plate halves. In another design, two separate plate halves are
stamped and then welded together so that anode flow channels are
provided at one side of one of the plate halves, cathode flow
channels are provided at an opposite side of the other plate half
and cooling fluid flow channels are provided between the plate
halves.
[0009] As is well understood in the art, the membranes within a
fuel cell need to have a certain relative humidity so that the
ionic resistance across the membrane is low enough to effectively
conduct protons. During operation of the fuel cell, moisture from
the MEAs and external humidification may enter the anode and
cathode flow channels. At low cell power demands, typically below
0.2 A/cm.sup.2, the water may accumulate within the flow channels
because the flow rate of the reactant gas is too low to force the
water out of the channels. As the water accumulates, it forms
droplets that continue to expand because of the relatively
hydrophobic nature of the plate material. The droplets form in the
flow channels substantially perpendicular to the flow of the
reactant gas. As the size of the droplets increases, the flow
channel is closed off, and the reactant gas is diverted to other
flow channels because the channels are in parallel between common
inlet and outlet manifolds. Because the reactant gas may not flow
through a channel that is blocked with water, the reactant gas
cannot force the water out of the channel. Those areas of the
membrane that do not receive reactant gas as a result of the
channel being blocked will not generate electricity, thus resulting
in a non-homogenous current distribution and reducing the overall
efficiency of the fuel cell. As more and more flow channels are
blocked by water, the electricity produced by the fuel cell
decreases, where a cell voltage potential less than 200 mV is
considered a cell failure. Because the fuel cells are electrically
coupled in series, if one of the fuel cells stops performing, the
entire fuel cell stack may stop performing.
[0010] A fuel cell stack typically includes a seal that extends
around the active area of the stack and between the stack headers
and the active area for each fuel cell to prevent gas leakage from
the stack. Therefore, in order to get the cathode flow, the anode
flow and the cooling fluid flow from the respective inlet header
into the active area of the fuel cell, it is necessary for the flow
channels to go through the seal area without affecting seal
integrity. Typically holes are provided through the bipolar plate
around the seals, which requires a bend in the flow channels so
that they line up with the flow channels in the active area. This
bend in the cathode and anode flow channels provided an area that
water could accumulate and be trapped which had a tendency to close
the flow channel and reduce the flow of reactant gas thereto.
Therefore, a better technique for traversing the seal area of the
fuel cell stack is needed.
SUMMARY OF THE INVENTION
[0011] In accordance with the teachings of the present invention, a
fuel cell stack is disclosed that includes straight cathode flow
channels and anode flow channels through a seal area between
bipolar plates in the stack. The fuel cell stack includes a seal
that extends around the active area of the fuel cells in the stack
and between the stack headers and the active area. At the locations
where the cathode flow channels extend through the seal area to the
cathode inlet header and the cathode outlet header, and the anode
flow channels extend through the seal area to the anode inlet
header and the anode outlet header, the diffusion media layer on
one side of the membrane is extended to provide the seal load.
[0012] Additional features of the present invention will become
apparent from the following description and appended claims, taken
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a fuel cell stack
including composite bipolar plates, according to an embodiment of
the present invention;
[0014] FIG. 2 is a cross-sectional view through line 2-2 of the
fuel cell stack shown in FIG. 1;
[0015] FIG. 3 is a cross-sectional view through line 3-3 of the
fuel cell stack shown in FIG. 1;
[0016] FIG. 4 is a cross-section view through line 4-4 of the fuel
cell stack shown in FIG. 1;
[0017] FIG. 5 is a cross-sectional view through line 5-5 of the
fuel cell stack shown in FIG. 1;
[0018] FIG. 6 is a cross-sectional view through line 6-6 of the
fuel cell stack shown in FIG. 1;
[0019] FIG. 7 is a cross-sectional view through line 7-7 of the
fuel cell stack shown in FIG. 1;
[0020] FIG. 8 is a cross-sectional view of a fuel cell stack
including composite bipolar plates and header seal loops, according
to another embodiment of the present invention;
[0021] FIG. 9 is a cross-sectional view through line 9-9 of the
fuel cell stack shown in FIG. 8;
[0022] FIG. 10 is a cross-sectional view through line 2-2 of the
fuel cell stack shown in FIG. 1, where the fuel cell stack includes
composite bipolar plates and shims;
[0023] FIG. 11 is a cross-sectional view through line 3-3 of the
fuel cell stack shown in FIG. 1 that includes composite bipolar
plates and shims;
[0024] FIG. 12 is a cross-sectional view through line 4-4 of the
fuel cell stack shown in FIG. 1 that includes composite bipolar
plates and shims;
[0025] FIG. 13 is a cross-sectional view through line 5-5 of the
fuel cell stack shown in FIG. 1 that includes composite bipolar
plates and shims;
[0026] FIG. 14 is a cross-sectional view through line 6-6 of the
fuel cell stack shown in FIG. 1 that includes composite bipolar
plates and shims;
[0027] FIG. 15 is a cross-sectional view through line 7-7 of the
fuel cell stack shown in FIG. 1 that includes composite bipolar
plates and shims;
[0028] FIG. 16 is a cross-sectional view of a fuel cell stack
including stamped bipolar plates, according to another embodiment
of the present invention;
[0029] FIG. 17 is a cross-sectional view through line 17-17 of the
fuel cell stack shown in FIG. 16;
[0030] FIG. 18 is a cross-sectional view through line 18-18 of the
fuel cell stack shown in FIG. 16;
[0031] FIG. 19 is a cross-sectional view trough line 19-19 of the
fuel cell stack shown in FIG. 16;
[0032] FIG. 20 is a cross-sectional view through line 20-20 of the
fuel cell stack shown in FIG. 16;
[0033] FIG. 21 is a cross-sectional view through line 21-21 of the
fuel cell stack shown in FIG. 16;
[0034] FIG. 22 is a cross-sectional view through line 22-22 of the
fuel cell stack shown in FIG. 16;
[0035] FIG. 23 is a cross-sectional view of a fuel cell stack
including stamped bipolar plates and header seal loops, according
to another embodiment of the present invention;
[0036] FIG. 24 is a cross-sectional view through line 24-24 of the
fuel cell stack shown in FIG. 23;
[0037] FIG. 25 is a cross-sectional view through line 17-17 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0038] FIG. 26 is a cross-sectional view through line 18-18 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0039] FIG. 27 is a cross-sectional view through line 19-19 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0040] FIG. 28 is a cross-sectional view through line 20-20 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0041] FIG. 29 is a cross-sectional view through line 21-21 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0042] FIG. 30 is a cross sectional view through line 22-22 of the
fuel cell stack shown in FIG. 16, where the stack includes stamped
bipolar plates and shims;
[0043] FIG. 31 is a cross-sectional view of a fuel cell stack
including stamped bipolar plates, where the bipolar plates provide
the seal for the stack, according to another embodiment of the
present invention;
[0044] FIG. 32 is a cross-sectional through line 32-32 of the fuel
cell stack shown in FIG. 31;
[0045] FIG. 33 is a cross-sectional view through line 33-33 of the
fuel cell stack shown in FIG. 31;
[0046] FIG. 34 is a cross-sectional view through line 34-34 of the
fuel cell stack shown in FIG. 31;
[0047] FIG. 35 is a cross-sectional view through line 35-35 of the
fuel stack shown in FIG. 31;
[0048] FIG. 36 is a cross-sectional view through line 36-36 of the
fuel cell stack shown in FIG. 31;
[0049] FIG. 37 is a cross-sectional view through line 37-37 of the
fuel cell stack shown in FIG. 31;
[0050] FIG. 38 is a cross-sectional view of a fuel cell stack
including stamped bipolar plates and header seal loops, where the
bipolar plates provide the seal for the stack, according to another
embodiment of the present invention;
[0051] FIG. 39 is a cross-sectional view through line 39-39 of the
fuel cell stack shown in FIG. 38;
[0052] FIG. 40 is a cross-sectional view through line 32-32 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack;
[0053] FIG. 41 is a cross-sectional view through line 33-33 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack;
[0054] FIG. 42 is a cross-sectional view through line 34-34 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack;
[0055] FIG. 43 is a cross-sectional view through line 35-35 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack;
[0056] FIG. 44 is a cross-sectional view through line 36-36 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack; and
[0057] FIG. 45 is a cross-sectional view through line 37-37 of the
fuel cell stack shown in FIG. 31, where the stack includes stamped
bipolar plates and shims, and where the bipolar plates provide the
seal for the stack.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0058] The following discussion of the embodiments of the invention
directed to a fuel cell stack including straight reactant gas flow
channels through a seal area is merely exemplary in nature, and is
in no way intended to limit the invention or applications or
uses.
[0059] FIG. 1 is a cross-sectional view through a fuel cell 50 of a
fuel cell stack 10, where the stack 10 includes an active area 12
and composite bipolar plates. The stack 10 includes a cathode inlet
header 14 that receives a cathode reactant gas flow and a cathode
outlet header 16 that receives a cathode outlet gas flow, where the
cathode gas flows through flow channels in the active area 12. The
stack 10 also includes an anode inlet header 18 that receives an
anode reactant gas flow and an anode outlet header 20 that receives
an anode exhaust gas flow, where anode flow channels extend through
the active area 12. The stack 10 also includes a cooling fluid
inlet header 22 that receives a cooling fluid and a cooling fluid
outlet header 24 that outputs the cooling fluid from the stack 10,
where the cooling fluid flows through cooling fluid channels
through the active area 12, as is well understood in the art.
[0060] In order to contain and separate the reactant gas flows and
the cooling fluid flow, various seals are provided between the
bipolar plates in the stack 10. Particularly, a seal 30 is provided
around the perimeter of the fuel cell 50, a seal 32 is provided
between the cathode inlet header 14 and the active area 12, a seal
34 is provided between the cathode outlet header 16 and the active
area 12, a seal 36 is provided between the anode inlet header 18
and the active area 12, a seal 38 is provided between the anode
outlet header 20 and the active area 12, a seal loop 40 is provided
around the cooling fluid inlet header 22, and a seal loop 42 is
provided around the cooling fluid outlet header 24. The seals can
be made of any suitable elastomeric or resilient material.
[0061] FIG. 2 is a cross-sectional view through line 2-2 of the
fuel cell 50. The fuel cell 50 includes an anode side composite
bipolar plate 52 and a cathode side composite bipolar plate 54. The
bipolar plates shown in the figures are bipolar plate halves in
that the bipolar plate half for the adjacent fuel cell is not
shown. The fuel cell 50 also includes an anode side diffusion media
layer 56, a cathode side diffusion media layer 58 and a membrane 60
therebetween. The anode side bipolar plate 52 includes anode flow
channels 62 and the cathode side bipolar plate 54 includes part of
cooling fluid flow channels 64, where the other half of the cooling
fluid flow channels is provided by the other plate half.
[0062] The seal 32 is positioned in a channel 66 in the anode side
bipolar plate 52. In the known fuel cell stacks that include
composite bipolar plates, the seal would be thicker and the
membrane 60 would follow a curved path around the seal. According
to the invention, the membrane 60 extends straight through the seal
area and the cathode side diffusion media layer 58 has been
extended to an outer edge of the cathode side bipolar plate 54. The
extended diffusion media layer 58 provides seal integrity at the
cathode side of the seal area. As a result of this configuration,
cathode flow channels 68 extending from the cathode inlet header 14
to the active area 12 are straight. The seal area between the
cathode outlet header 16 and the active area 12 would look the
same.
[0063] FIG. 3 is a cross-sectional view through line 3-3 of the
fuel cell stack 10 showing the seal area between the anode inlet
header 18 and the active area 12 of the fuel cell 50. According to
the invention, the seal 36 is narrower and the anode side diffusion
media layer 56 has been extended to an outer edge of the anode side
bipolar plate 52. The extended diffusion media layer 56 provides
seal integrity at the anode side of the seal area. Further, the
anode flow channels 62 extending from the header 18 to the active
area 12 are straight. The seal area between the anode outlet header
20 and the active area 12 would look the same.
[0064] FIG. 4 is a cross-sectional view through line 4-4 of the
fuel cell stack 10 showing the seal area between the cooling fluid
inlet header 22 and the active area 12. At this location, the seal
30 includes cathode and anode seal halves 72 and 74 and the seal 40
includes cathode and anode seal halves 76 and 78. Straight flow
cooling fluid channels 64 are provided from the cooling fluid inlet
header 22 to the active area 12 through the seal area. The
cross-sectional view of the fuel cell 50 at this location would be
nearly the same as some of those known in the art. The seal area
between the cooling fluid outlet header 24 and the active area 12
would look the same.
[0065] FIG. 5 is a cross-sectional view through line 5-5 showing a
joint sealing area between the cathode outlet header 16 and the
active area 12. In the joint area, a gap 70 may be created between
the diffusion media layer 58 and the seal 30 where the diffusion
media layer 58 is supporting the seal on the opposite side of the
membrane 60. The gap 70 itself is not a sealing issue as flow is
passing through this region anyway. It may be necessary to provide
a continuous surface for the seal on the opposite side of the
membrane 60 to seal against. Thus, a filling material may be
provided in the gap 70 to provide seal support. The filling
material may be an elastometer that cures in place after the seal
30 and the diffusion media layer 58 have been positioned. If a
membrane with sub-gaskets support is sufficiently stiff, it can
bridge the gap 70 without loss of seal function, and a fill
material may not be required. An alternative solution for dealing
with the gap 70 is to nest the header seal as a complete loop
within a separate and continuous perimeter loop. At this location,
the diffusion media layer 58 has been extended, as discussed
above.
[0066] FIG. 6 is a cross-sectional view through line 6-6 of the
fuel cell stack 10 at an edge of the active area 12. At this
location, the seal 30 includes the two seal halves 72 and 74. The
cross-sectional view of the fuel cell 50 at this location would
also be about the same as some of those known in the art.
[0067] FIG. 7 is a cross-sectional view through line 7-7 of the
fuel cell stack 10 at an outer edge of the cathode outlet header
16. At this location, the seal 30 includes the two seal halves 72
and 74. The cross-sectional view of the fuel cell 50 at this
location would also be about the same as some of those known in the
art.
[0068] As discussed above, the diffusion media layers carry the
seal load across the channels in their reactant gas inlet and
outlet regions. If necessary, the diffusion media layer in the seal
support region can be filled to provide additional stiffness. This
allows direct channels into the active area 12 without tunnels or
ports, and does not require that holes be fabricated into the plate
or additional bridge inserts be provided. Eliminating the ports and
tunnels in the plates will improve water management as water has
been found to accumulate in these places. Further, eliminating the
holes in the plates simplifies the plate fabrication. Without
tunnels, only one side of the plate needs to have a hydrophilic
coating applied thereto.
[0069] At those locations where both the anode and cathode seals
overlap, both reactant gases are sealed. The cathode reactant gas
can flow through the anode seal where there is no cathode seal, so
a flow path from the cathode inlet header 14 to the cathode outlet
header 16 is provided. Similarly, the anode reactant gas flow can
pass the cathode seal where there is no anode seal, so a flow path
from the anode inlet header 18 to the anode outlet header 20 is
provided. For the solid composite plate design, the cooling fluid
flow path is independently defined from the reactant flow pattern
so that the cooling fluid channels 64 can pass between the seals
without affecting the sealing surface on the reactant gas sides.
The two plate halves would be bonded together to prevent leakage of
cooling fluid from between the plate halves. For solid plates, this
bond is not shown as the plate halves would typically be bonded
over the entire plate-to-plate interface surface to ensure low
electrical contact resistance between the two bipolar plate
halves.
[0070] In certain fuel cell designs, the anode headers and the
cathode headers include seal loops that extend completely around
the header to increase the seal integrity. FIG. 8 is a
cross-sectional view of a fuel cell stack 80 through a fuel cell
82, where like elements to the fuel cell stack 10 are identified by
the same reference numeral. In this fuel cell stack design, the
seal 32 at the cathode inlet header 14 is replaced with a seal loop
84, the seal 34 at the cathode outlet header 16 is replaced with a
seal loop 86, the seal 36 at the anode inlet header 18 is replaced
with a seal loop 88, and the seal 38 at the anode outlet header 20
is replaced with a seal loop 90.
[0071] The seal area between the cathode headers 14 and 16 and the
active area 12, the seal area between the anode headers 18 and 20
and the active area 12 and the seal area between the cooling fluid
headers and the active area 12 for the fuel cell stack 80 where the
diffusion media layers 56 and 58 are extended to provide the seal
integrity is the same as those seal areas in the fuel cell stack
10. However, the seal area at the outer edge of the headers 14, 16,
18 and 20 where there is an extra seal would be different. To show
this, FIG. 9 is a cross-sectional view through line 9-9 of the fuel
cell stack 80, according to an embodiment of the present invention.
The fuel cell 82 includes an anode side bipolar plate 92, a cathode
side bipolar plate 94, and a membrane 96 therebetween. Because the
cathode side diffusion media layer 98 would extend to the edge of
the header 16, the diffusion media layer 98 is shown extending
through the seal area provided by the seal loop 86 to provide the
continuous seal integrity.
[0072] It is know in the art to provide shims between the seal and
the membrane at the seal area. However, it has not been known to
use shims across channels to create tunnels and support seal loads.
According to another embodiment of the invention, a separate shim
could be used in this region in place of extending the diffusion
media layer for seal support. To ensure adequate seal support, a
thicker shim (about 0.1 mm) may be required that would be a larger
thickness change to accommodate a seal joint. To address this, the
shim could be continuous around the seal perimeter. It may be
preferable that the shims and seals be bonded to the membrane. This
approach could use shims on both sides, or only on one side.
Thinner sub-gaskets may be used on one or both sides as required to
provide the desired active area edge architecture. If only one shim
were used, a sub-gasket would be desired on the opposite side of
the membrane if material requirements do not allow membranes and
seals to have direct contact. For the shim supported configuration
with an elastomer seal, a span region may be provided. This simply
means that the span created by the gasket gland should be smaller
than a typical channel span (0.5-1.5 mm) as the shim must provide
adequate stiffness to support across a channel span. If the seals
are bonded to the shims and the membrane, the seal itself will
provide additional stiffness to the sealing surface as this surface
would be against the plate, and not the membrane, in this
configuration. Because these are shim supported rather than
diffusion media supported seals, the channels in this region may be
deeper at the shim because the shim is not as thick as the
diffusion media layer. The channel bottom could also rise in this
region to maintain channel size.
[0073] Most membranes have a thin (25 .mu.m) sub-gasket (plastic
film) on both sides around the perimeter for mechanical strength
and to avoid direct contact between the acidic ionomer membrane and
the plate or seals. The use of shims for the invention could
involve using a thicker sub-gasket(s) to provide adequate stiffness
to span channels and support seal loads.
[0074] FIGS. 10-15 show cross-sectional views through a fuel cell
110 of a fuel cell stack that would be similar to the fuel stack 10
where the various headers are provided at the same location of the
fuel cell stack and identified with the same reference numeral.
FIG. 10 represents a cross-sectional view at location 2-2 of the
fuel cell 110, FIG. 11 represents a cross-sectional view at
location 3-3 of the fuel cell 110, FIG. 12 represents a
cross-sectional view at location 4-4 of the fuel cell 110, FIG. 13
represents a cross-sectional view through location 5-5 of the fuel
cell 110, FIG. 14 represents a cross-sectional view at location 6-6
of the fuel cell 110, and FIG. 15 represents a cross-sectional view
of the fuel cell 110 at location 7-7.
[0075] FIG. 10 shows the seal area between the active area 12 of
the fuel cell 110 and the cathode inlet header 14. The fuel cell
110 includes an anode side bipolar plate 112, a cathode side
bipolar plate 114 and a membrane 116 therebetween. An anode side
diffusion media layer 118 is provided between the bipolar plate 112
and the membrane 116 on the anode side and a cathode side diffusion
media layer 120 is provided between the membrane 116 and the
bipolar plate 114 on the cathode side. Anode flow channels 132 are
provided in the anode side bipolar plate 112 and cooling fluid flow
channels 134 are provided in the cathode side bipolar plate
114.
[0076] In this embodiment, a shim 122 is provided between the
membrane 116 and an anode seal 124 at the seal area and a shim 126
is provided between the membrane 116 and a raised portion 128 of
the cathode side bipolar plate 114. Cathode flow channels 130
extend through the raised portion 128 and provides a straight flow
through the seal area to the active area 12 of the fuel cell 110.
The combination of the shim 126 and the raised portion 128 maintain
the seal integrity of the cathode side of the fuel cell 110 at this
location.
[0077] FIG. 11 shows the seal area between the active area 12 of
the fuel cell 110 and the anode inlet header 18 where the anode
side bipolar plate 112 includes a raised portion 140. The
combination of the raised portion 140 and the shim 122 provides the
structure to maintain the seal integrity at this area so that the
anode flow channels 132 have a straight flow through the seal area
of anode header 18 to the active area of the fuel cell 110. The
cathode side bipolar plate 114 includes a channel 144 in which a
seal 146 is positioned.
[0078] FIG. 12 shows shims 152 and 154 between seal halves 148 and
150 and the membrane 116 at the cooling fluid inlet header 22. The
cooling fluid flow channels 134 are shown in this
cross-section.
[0079] FIG. 13 shows shims 160 and 162 between the membrane 116 and
seals 164 and 166 at the joint area between the cooling fluid
outlet header 24 and the cathode outlet header 14.
[0080] FIG. 14 shows shims 170 and 172 between the membrane 116 and
seal halves 174 and 176 at the outer edge of the active area of the
fuel cell 110.
[0081] FIG. 15 shows shims 180 and 182 between seal halves 184 and
186 and the membrane 116 at an outer edge of the cathode outlet
header 16.
[0082] FIG. 16 is a cross-sectional view of a fuel cell stack 200
through a fuel cell 202 of the stack 200. In this embodiment, the
fuel cell stack 200 includes stamped bipolar plates. The fuel cell
stack 200 includes an active area 204, a cathode inlet header 206,
a cathode outlet header 208, an anode inlet header 210, an anode
outlet header 212, a cooling fluid inlet header 214, and a cooling
fluid outlet header 216. In an alternate embodiment, the fuel cell
stack 200 could include bonds that cross the seals, as is well
understood to those skilled in the art. A seal 220 extends around
an outer perimeter of the fuel cell 202. Further, a seal 222 is
provided between the cathode inlet header 206 and the active area
204, a seal 224 is provided between the cathode outlet header 208
and the active area 204, a seal 226 is provided between the anode
inlet header 210 and the active area 204, a seal 228 is provided
between the anode outlet header 212 and the active area 204, a seal
230 is provided between the cooling fluid inlet header 214 and the
active area 204, and a seal 232 is provided between the cooling
fluid outlet header 216 and the active area 204.
[0083] FIG. 17 is a cross-sectional view through line 17-17 of the
fuel cell 200. The fuel cell 200 includes an anode side stamped
bipolar plate 240 and a cathode side stamped bipolar plate 242. The
bipolar plates shown are bipolar plates halves in that the stamped
bipolar plate for the adjacent fuel cell is not shown. The fuel
cell 200 includes an anode side diffusion media layer 244, a
cathode side diffusion media layer 246 and a membrane 248
therebetween. The anode side bipolar plate 240 includes anode flow
channels 250 and part of cooling fluid flow channels 252, where the
other half of the cooling fluid flow channels are provided by the
other plate half. Plate bonds 238 are provided to bond the bipolar
plates together.
[0084] The seal 222 is provided at an outer edge of the anode side
of the bipolar plate 240. According to the invention, the seal 222
is thinner than the seal that would normally be present at this
location so that the membrane 248 is straight through the seal
area. Further, the cathode side diffusion media layer 246 has been
extended to an outer edge of the cathode side bipolar plate 242 to
provide seal integrity at the cathode side of the seal area. By
extending the diffusion media 246 in this manner, cathode flow
channels 254 can be straight through the seal area into the active
region 204 to reduce areas where water can accumulate in the flow
channels 254. The seal area between the cathode outlet header 208
and the active area 204 would look the same.
[0085] FIG. 18 is a cross-sectional view through line 18-18 of the
fuel cell stack 200 showing the seal area between the anode inlet
header 210 and the active area 204 of the fuel cell 202. According
to the invention, the seal 226 is reduced in thickness from the
seal that would normally be provided at this location so that the
membrane 248 extends straight through the seal area from the active
region 204. Further, the anode side diffusion media layer 244 is
extended through the seal area so that the anode flow channels 250
extend straight through the seal area for the purposes discussed
above. The seal area between the anode outlet header 212 and the
active area 204 would look the same.
[0086] FIG. 19 is a cross-sectional view through line 19-19 of the
fuel cell stack 200 showing the seal area between the cooling fluid
inlet header 214 and the active area 204. According to the
invention, the thickness of the seals 230 and 220 are reduced so
that the membrane 248 extends straight through the seal area from
the cooling fluid inlet header 214 to the active area 204. The seal
area between the cooling fluid outlet header 216 and the active
area 204 would look the same.
[0087] FIG. 20 is a cross-sectional view through line 20-20 of the
fuel cell stack 200 showing a joint sealing area between the
cathode outlet header 208 and the active area 204. In this
embodiment, the anode side diffusion media layer 246 has been
extended to the seal 220, as shown. A gap 264 is provided between
the diffusion media layer 246 and the seal 220, and can be filled
with appropriate filling material. In this configuration, the
membrane 248 extends straight through the seal area.
[0088] FIG. 21 is a cross-sectional view through line 21-21 of the
fuel cell stack 200 at an edge section of the fuel cell 202. In
this embodiment, the seal 220 includes two seal halves 270 and 272
that allow the membrane 248 to extend straight through the seal
area into the active area 204.
[0089] FIG. 22 is a cross-sectional view through line 22-22 of the
fuel cell stack 200 at an outer edge portion of the cathode outlet
header 208. In this embodiment, the seal 220 is made of the two
seal halves 270 and 272 to provide the straight membrane 248
through the seal area.
[0090] For the stamped plates, a bond is shown where the plate
halves need to be sealed together to prevent cooling fluid
leakages. This could be done using a welded or adhesive bond. For
stamped plates with elastomer seals, an option would be for the
bond lines to traverse the seal glands. To ensure adequate seal
support for the stamped plates, the plate halves contact each other
on either side of the seal. In the cooling fluid inlet header 214,
the cooling fluid flow path is provided so that the plate halves
shown by the dotted lines show this. The cooling fluid can flow
through because the path is not blocked by the plates. Also for the
stamped plate configuration with elastomer seals, the cathode seal
is shown to be more inboard on both ends, but seal order with
respect to the flow direction is not critical and may be defined
based on other requirements.
[0091] In another fuel cell design, the anode headers, the cathode
headers and the cooling fluid headers may include seal loops that
extend completely around the header to increase the seal integrity.
FIG. 23 is a cross-sectional view of a fuel cell stack 280 through
a fuel cell 282, where like elements to the fuel cell stack 200 are
identified by the same reference numeral, according to another
embodiment of the present invention. In this fuel cell stack
design, the seal 222 at the cathode inlet header 206 is replaced
with a seal loop 286, the seal 224 at the cathode outlet header 208
is replaced with a seal loop 288, the seal 226 at the anode inlet
header 210 is replaced with a seal loop 290, the seal 228 at the
anode outlet header 212 is replaced with a seal loop 292, the seal
230 at the cooling fluid inlet header 214 is replaced with seal
loops 294 and 296, and the seal 232 at the cooling fluid outlet
header 216 is replaced with seal loops 298 and 300. As the
motivation for the header loops is to avoid joints, such as shown
by FIG. 20, which only appear at the corners of the reactant
headers adjoining the active area, the coolant headers can be
maintained without loops, as shown in FIG. 16.
[0092] The seal areas between the headers and the active area of
the fuel cell stack 280 where the diffusion media layers 244 and
246 are extended to provide the seal integrity is the same as those
areas in the fuel cell stack 200. However, the seal area at the
outer edge of the headers where there is an extra seal would be
different. To show this, FIG. 24 is a cross-sectional view through
line 24-24 of the fuel cell stack 280. The fuel cell 282 includes
an anode side bipolar plate 302, a cathode side bipolar plate 304
and a membrane 306 therebetween. Because the anode side diffusion
media layer 308 would extend to the edge of the header 208, a
cathode side diffusion media layer 308 is shown extending through
the seal area provided by the seal loop 288 to provide the
continuous seal integrity. In this embodiment, the outer seal loop
220 is made up of two seal halves 310 and 312 at this location.
[0093] As discussed above, it is known in the art to provide shims
between the seal and the membrane of the seal area, but it is not
known to use shims across channels to create tunnels and support
seal loads. FIGS. 25-30 show cross-sectional views through a fuel
cell 320 of a fuel cell stack that would be similar to the fuel
cell stack 200 where the various headers are provided at the same
location of the fuel cell stack. Thus, FIG. 25 represents a
cross-sectional view at location 17-17 of the fuel cell 320, FIG.
26 represents a cross-sectional view at location 18-18 of the fuel
cell 320, FIG. 27 represents a cross-sectional view at location
19-19 of the fuel cell 320, FIG. 28 represents a cross-sectional
view at location 20-20 of the fuel cell 320, FIG. 29 represents a
cross-sectional view at location 21-21 of the fuel cell 320 and
FIG. 30 represents a cross-sectional view at location 22-22 of the
fuel cell 320.
[0094] The fuel cell 320 includes an anode side stamped bipolar
plate 322, a cathode side stamped bipolar plate 324 and a membrane
326 therebetween. An anode side diffusion media layer 328 is
provided between the bipolar plate 322 and the membrane 326 and a
cathode side diffusion media layer 330 is provided between the
membrane 326 and the bipolar plate 324. The anode side bipolar
plate 322 defines anode side flow channels 340 and cooling fluid
channels 342. In this embodiment, a shim 332 is provided between
the membrane 326 and a seal 334 at the seal area and a shim 336 is
provided between the membrane 326 and a raised portion 338 of the
cathode side bipolar plate 324. Cathode flow channels 344 extend
around the raised portion 338 and provide a straight flow through
the seal area to the active area of the fuel cell 320. The
combination of the shim 336 and the raised portion 338 maintain the
seal integrity of the cathode side of the fuel cell 320 at this
location.
[0095] FIG. 26 shows a seal area between the active area of the
fuel cell 320 and the anode inlet header where the anode side
bipolar plate 322 includes a raised portion 346. A shim 348 is
provided between the raised portion 346 and the membrane 326 and a
shim 350 is provided between the membrane 326 and a seal 352. The
combination of the raised portion 346 and the shim 348 provides the
structure to maintain the seal integrity at this area so that the
anode flow channels 340 have a straight line flow through the seal
area from the anode inlet header to the active area of the fuel
cell 320.
[0096] FIG. 27 shows shims 354 between the seal 220 and the anode
side bipolar plate 322, a shim 356 between the membrane 326 and the
anode side bipolar plate 322 and a shim 358 between the membrane
326 and the seal 230.
[0097] FIG. 28 shows a shim 360 between the seal 224 and the
membrane 326 and a shim 362 between the seal 220 and the membrane
326.
[0098] FIG. 29 shows a shim 364 between the seal 270 and the
membrane 326 and a shim 366 between the membrane 326 and the seal
272.
[0099] FIG. 30 shows a shim 368 between the seal half 270 and the
membrane 326, and a shim 370 between the membrane 326 and the seal
half 272.
[0100] FIG. 31 is a cross-sectional view of a fuel cell stack 380
through a fuel cell 382. In this embodiment, the fuel cell stack
380 includes stamped bipolar plates, where the plates themselves
provide the seal. The fuel cell stack 380 includes an active area
384, a cathode inlet header 386, a cathode outlet header 388, an
anode inlet header 390, an anode outlet header 392, a cooling fluid
inlet header 394 and a cooling fluid outlet header 396. A seal 398
extends around the perimeter of the fuel cell 382. A seal 400 is
provided between the cathode inlet header 386 and the active area
384, a seal 402 is provided between the cathode outlet header 388
and the active area 384, a seal 404 is provided between the anode
inlet header 390 and the active area 384, a seal 406 is provided
between the anode outlet header 392 and the active area 384, a seal
408 is provided between the cooling fluid inlet header 394 and the
active area 384 and a seal 410 is provided between the cooling
fluid outlet header 396 and the active area 384. As mentioned
above, all of the seals in this design are provided by the
configuration of the bipolar plate.
[0101] FIG. 32 is a cross-sectional view through line 32-32 of the
fuel cell 382. The fuel cell 382 includes an anode side stamped
bipolar plate 420 and a cathode side stamped bipolar plate 422. The
fuel cell 382 also includes an anode side diffusion media layer 424
and a cathode side diffusion media layer 426 with a membrane 428
therebetween. The anode side bipolar plate 420 includes anode flow
channels 430 and half of cooling fluid flow channels 432, where the
other half of the cooling fluid flow channels is provided by the
other stamped plate half.
[0102] The seal 400 is defined by a section of the anode side
bipolar plate 420. According to the invention, the cathode side
diffusion media layer 426 is extended through the seal area
opposite to the seal 400 to provide the seal integrity at this side
of the membrane 428. Thus, cathode flow channels 434 can extend
straight through the seal area from the cathode inlet header 386 to
the active area 384 so that they do not have to jog around plate
components that would act to collect water. The seal area between
the cathode outlet header 388 and the active area 384 would look
the same.
[0103] FIG. 33 is a cross-sectional view through line 33-33 of the
fuel cell 382 showing the seal area between the anode inlet header
390 and the active area 384 of the fuel cell stack 380. According
to the invention, the anode side diffusion media layer 424 is
extended at this location to provide the seal integrity at the
anode side of the fuel cell 382 opposite to the seal 404 provided
by the structural configuration of the bipolar plate 422. The seal
area between the anode outlet header 392 and the active area 384
would look the same.
[0104] FIG. 34 is a cross-sectional view through line 34-34 of the
fuel cell stack 380 showing the seal area between the cooling fluid
inlet header 394 and the active area 384. At this location of the
fuel cell 382, the anode side bipolar plate 420 and the cathode
side bipolar plate 422 provide the seals 408 and 398. The cooling
fluid flow channels 432 extend through the plate in a straight flow
through the seal area to the active area 384. Because the plates
420 and 422 provide the seals in this embodiment, this brings
adjacent bipolar plates into electrical contact at certain
locations in the fuel cell 382 and would create an electrical
short. Therefore, a non-conductive separator 438 is provided at the
seal location 408 to prevent electrical shorting. The seal area
between the cooling fluid outlet header 396 and the active area 384
would look the same.
[0105] FIG. 35 is a cross-sectional view through line 35-35 at a
joint sealing area between the cathode outlet header 388 and the
active area 384. The cathode side diffusion media layer 426 is
extended at this location for the anode side bipolar plate 420 and
the cathode side bipolar plate 422 define the seals 402 and 398. A
gap 440 between the diffusion media layer 426 and the seal portion
of the plate 422 may need to be filled with a suitable
material.
[0106] FIG. 36 is a cross-sectional view at an edge section of the
fuel cell 382, and would be similar to the edge section of the
known fuel cell stacks that include stamped bipolar plates with
stamped seals.
[0107] FIG. 37 is a cross-sectional view through line 37-37 of the
fuel cell stack 380 at an outer edge of the cathode outlet header
388. At this location, the seal 398 is provided by the anode side
bipolar plate 420 and the cathode side bipolar plate 422.
[0108] For certain fuel cell designs, as discussed above, the anode
headers, the cathode headers and the cooling fluid headers include
seal loops that extend completely around the header to increase the
seal integrity. FIG. 38 is a cross-sectional view of a fuel cell
stack 450 through a fuel cell 452, where like elements to the fuel
cell stack 380 are identified by the same reference numeral. In
this fuel cell stack design, the seal 400 at the cathode inlet
header 386 is replaced with a seal loop 454, the seal 402 at the
cathode outlet header 388 is replaced with a seal loop 456, the
seal 404 at the anode inlet header 390 is replaced with a seal loop
458, the seal 406 at the anode outlet header 392 is replaced with a
seal loop 460, the seal 408 at the cooling fluid inlet header 394
is replaced with a seal loop 462 and the seal 410 at the cooling
fluid outlet header 396 is replaced with a seal loop 464. As the
motivation for the header loops is to avoid joints, such as shown
by FIG. 35, which only appear at the corners of the reactant
headers adjoining the active area, the coolant headers can be
maintained without loops, as shown in FIG. 31.
[0109] The seal area between the cathode headers 386 and 388 and
the active area 384, between the anode headers 390 and 392 and the
active area 384 and between the cooling fluid headers 394 and 396
and the active area 384 is the same as those seal areas in the fuel
cell stack 380. However, the seal area at the outer edge of the
headers 386, 388, 390, 392, 394 and 396 where there is an extra
seal would be different. To show this, FIG. 39 is a cross-sectional
view through line 39-39 of the fuel cell stack 450, according to
another embodiment of the present invention. The fuel cell 452
includes an anode side bipolar plate 470, a cathode side bipolar
plate 472 and a membrane 474 therebetween. Because the cathode side
diffusion media layer 476 would extend to the edge of the header
388, the diffusion media layer 476 is shown extending through the
seal area provided by the seal loop 456 to provide the continuous
seal integrity.
[0110] As discussed above, it is known in the art to provide shims
between the seal and the membrane seal area. FIGS. 40-45 show
cross-sectional views through a fuel cell 500 that would be similar
to the fuel cell 382 where the various headers are provided at the
same location of the fuel cell stack 380. FIG. 40 represents a
cross-sectional view at location 32-32 of the fuel cell 500, FIG.
41 represents a cross-sectional view at location 33-33 of the fuel
cell 500, FIG. 42 represents a cross-sectional view at location
34-34 of the fuel cell 500, FIG. 43 represents a cross-sectional
view at location 35-35 of the fuel cell 500, FIG. 44 represents a
cross-sectional view at location 36-36 of the fuel cell 500 and
FIG. 45 represents a cross-sectional view of the fuel cell 500 at
location 37-37.
[0111] FIG. 40 shows the seal area between the active area 384 of
the fuel cell 500 and the cathode inlet header 386. The fuel cell
500 includes an anode side bipolar plate 502, a cathode side
bipolar plate 504 and a membrane 506 therebetween. An anode side
diffusion media layer 508 is provided between the bipolar plate 502
and the membrane 506 and a cathode side diffusion media layer 510
is provided between the membrane 506 and the bipolar plate 504. The
anode side bipolar plate 502 defines anode flow channels 522 and
cooling fluid flow channels 524. In this embodiment, a shim 512 is
provided between the membrane 506 and a seal section 514 of the
plate 502 and a shim 516 is provided between the membrane 506 and a
seal section 518. Cathode flow channels 520 extend through the seal
area and provide a straight flow to the active area of the fuel
cell 500.
[0112] FIG. 41 shows the seal area between the active area 384 of
the fuel cell 500 and the anode inlet header 390. A shim 530 is
provided between a seal section 532 of the plate 502 and the
membrane 506, and a shim 534 is provided between a seal section 536
of the plate 504 and the membrane 506.
[0113] FIG. 42 shows the seal area between the active area of the
fuel cell 500 and the cooling fluid inlet header 394. A shim 540 is
provided between a seal section 542 of the bipolar plate 502 and a
separator 538, and a shim 544 is provided between a seal section
546 of the cathode side bipolar plate 504 and the separator 538.
Likewise, a shim 550 is provided between a seal portion 552 of the
plate 502 and the membrane 506, and a shim 554 is provided between
a seal section 556 and the membrane 506. The cooling fluid flow
channels 524 extend through the plates 502 and 504 in a straight
flow though the seal area to the active area.
[0114] FIG. 43 shows a shim 560 between a seal portion 562 of the
anode side bipolar plate 502 and the membrane 506 and a shim 564
between a seal section 566 of the plate 504 of the cathode side
bipolar plate 504 and the membrane 506.
[0115] FIG. 44 shows a shim 570 between a seal section 572 of the
anode side bipolar plate 502 and a shim 574 between a seal section
576 of the cathode side bipolar plate 504 and the membrane 506.
[0116] FIG. 45 shows a shim 580 positioned between a seal section
582 of the anode side bipolar plate 502 and the membrane 506, and a
shim 584 positioned between a seal section 586 of the cathode side
bipolar plate 504 and the membrane 506.
[0117] The foregoing discussion discloses and describes merely
exemplary embodiments of the present invention. One skilled in the
art will readily recognize from such discussion and from the
accompanying drawings and claims that various changes,
modifications and variations can be made therein without departing
from the spirit and scope of the invention as defined in the
following claims.
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